1. Field of the Invention
The present invention relates generally to an optical lens assembly, and more particularly to a focusing-free microlens assembly and the method of making the same.
2. Description of the Related Art
A conventional optical lens has a constant focus, a constant depth of field and a constant depth of focus. In a condition of keeping an image with a constant depth of focus, the depth of focus is defined as a permitted distance of the focus moving along an optical axis of the lens, in which the lens may catch a clear image.
As shown in FIG. 1, a conventional image catch unit 1 includes a lens assembly 2 and an image sensor 3. The lens assembly 2 is mounted on the image sensor 3. The lens assembly 2 includes a plurality of lenses 4, a barrel 5 and a holder 6. The lenses 4 adhere to the barrel 5, and then the barrel 5 is fixed on the holder 6. At least, the holder 6 adheres to the image sensor 3. The image sensor 3 is kept in the depth of focus. Because of the tolerance of each component of the image catch unit, it always causes a change of focus, unable focusing and some other problem when these components are assembled together. It makes the image catch unit 1 having a high ratio of defective and needing focusing adjustment that making the process of fabrication complex.
An improved lens assembly with a focusing-free function includes a lens mask, a lens, a base and an image sensor. The lens mask is mounted at a position, on which the lens and the image sensor in the mask have an optimal focus therebetween to transfer the image directly to the image sensor via the lens without focusing adjustment.
However, the components of above improved lens assembly still have tolerances respectively. These tolerances cause a change of focus also that the lens assembly has a bad function of focusing-free.